Automatic systems for handling many tape cartridges (cassettes) in conjunction with one or more tape drives are becoming more and more important in the world of data storage, such as tape back-ups for computer systems. Such systems are typically called a “loader” if the systems contain one tape drive and a small number (5-16) of tape cartridges; and are typically called a “library” if the systems contain two or more drives (and normally from 10 cartridges and upwards). These systems are designed to meet the need for reliable, low cost data backup and retrieval in modern data storage systems. With the systems, one is able to select any one of all the cartridges in the automation system and automatically insert it into one or more of the tape drives, and then later replace the selected cartridge with the next cartridge needed for the system operation. With such systems, operator handling, which is costly, as well as operator mistakes, can be drastically reduced.
A common name for tape loaders and tape libraries is “tape automation systems”, which is used hereafter. Also in the following, the word “cartridge” is used to cover both tape cassettes and tape cartridges.
Although the actual designs may vary significantly, a typical tape automation system 10 contains the following main items as shown in FIG. 1: a cabinet 100, one or more tape drives 101, one or more magazines 102 which each may contain a number of cartridges 103, a cartridge picker (robot) 104 which can take any cartridge from the magazines 102 and put into one of the tape drives 101 or vice versa. An example of this system is shown in U.S. Pat. No. 6,829,116, which shows in detail a prior art rotating cartridge picker. Larger systems may also have a system for lifting the cartridge picker to a different height to allow it to pick a cartridge from another magazine, or from another position within the same magazine.
Additionally, the tape automation systems contain some form of electrical control system 106 which controls the operation of the tape drive 101 and the cartridge picker 104, as well as communicating with a connected host computer. A power supply 107 supplies electric power for the entire unit.
The operation of a typical low end tape automation system having one tape drive 101 and just one or two magazines 102 is described hereafter, with reference to FIG. 1.
The specially designed magazine 102 containing the tape cartridges 103 is placed inside the tape automation system 10. the electrical control system 106 will (based on commands from the connected computer host), send signals to the cartridge picker 104 which moves along rail or rails 90A,B to pick a specific cartridge 103 from the magazine 102 and insert it into the tape drive 101. The tape drive 101 will then execute one or more active commands on the cartridge (reading/writing/winding etc.). When the tape drive 101 has finished its operations on the inserted cartridge 103, it will eject the cartridge from the tape drive 101. the cartridge 103 is then grabbed by the picker 104 and put back into the magazine. Then the cartridge picker 104 will take another cartridge 103 from the magazine, place it into the tape drive 101, and the operation continues. Note the cartridge picker operates in two main axis, X and Y. The X-direction is defined as the direction in and out of the tape drive, while Y is in the direction in and out of the magazines. In addition, the cartridge picker is able to rotate around its vertical axis (with a cartridge) so that the cartridge front either is positioned to be moved in or out of the tape drive (the X direction) or in or out of a room of the magazine (the Y axis).
An automation system having several tape drives and magazines stacked on top of each other operates in the same manner, except that the picker 104 then has to move up and down between several levels of magazines and tape drives. FIG. 2 shows how cartridges 103 are stacked above each other with a stack of magazines 102. FIG. 15 of U.S. Pat. No. 6,829,116 also shows this. A small locking arm or finger 108 prevents the cartridge from falling out when the magazine is carried around. The magazine itself can be one single unit with storage rooms for all the specified cartridges, or the system can be designed to accept several magazines 102 (each typically with one or two levels of cartridges) stacked upon each other. Likewise the tape drives 101 (FIG. 1) can be stacked upon each other. In this case, the automation system will normally be equipped with a cartridge picker 104 (FIG. 1) that can move along all three main axes. In addition to the operation along the x and y axis described above in FIG. 1, the cartridge picker typically has a built-in elevator system to allow movement along the vertical Z axis of a cartridge inside the picker 102 to a specific tape drive level or cartridge room level.
Thus, in almost all low end automation systems, the cartridge picker is guided by a rail or a set of rails 90A,B as shown in FIG. 1. These rails 90 are normally mounted to the bottom plate 80 of the automation unit 10, and the cartridge picker 104 can run along the rails. To move to different heights within an automation system of the type shown in FIG. 2, the cartridge picker has a built-in elevator that can lift either almost the complete picker system or just the cartridge picker 104 itself up to the various heights within the automation system.
Compared to using a single drive, the tape automation system makes it possible to increase total storage capacity with anywhere from a typical factor of 7 up to upwards of many 1000's for the largest and most complex systems, with human handling and interference being reduced to a bare minimum.
Over the years, many forms and variations of automation systems have emerged; however, in the low end arena of the automation systems, more and more systems are now based on the same principle configuration as shown in FIG. 1.
From a physical size point of view, these systems are designed to fit into 19″ wide racks, and come in fixed height sizes: 1 U (as shown on FIG. 1), 2 U, 3 U, 4 U (as shown in FIG. 2) and so on. Each “U” (=“unit”) means a height dimension of 1.75″ or 41.5 mm. A 1 U system typically contains one tape drive and 4-8 cartridges in one or two magazines (see FIG. 1). The magazine stack shown in FIG. 2 will typically be part of a 4 U level system. Except for the 1 U systems, other systems (2 U and above) normally need to have a picker system designed so that the portion of the picker handling the cartridge can be moved up and down between the various levels, (normally done with a built-in elevator in the picker).
Low end systems are normally designed so that they are not expandable, meaning that they are designed for a fixed number of tape drives and cartridges. However, the actual number of drives and cartridges at the time of purchase may vary. For example, a typical 4 U system may contain two magazine groups, each with 4 levels and 4 cartridges on each level. It may also have space for up to four drives. However, the user may elect to buy the system with just one drive and for example only one group of magazines and cartridges (in this example then 16 cartridges). The user may then later install more magazines to bring the total number of available cartridge slots up to the maximum (in this case 32) and also install more tape drives (in this case up to a maximum of 4).
Should the user later need more capacity, he or she typically will have to buy a new automation system and connect this to the same computer. The two automation systems will operate independently of each other; however, both will (normally) be controlled by the same computer host.
As shown in FIG. 3, there exist prior art low end automation systems that are designed to be stacked upon each other and have a special lift or elevator 111 at an end of the system, so that cartridges from one automation unit can be passed up or down to the other unit. Here, two complete automations systems 109 and 110 are stacked upon each other. FIG. 3 shows the two units as seen from the side. At the back of the two units is mounted the “pass-thru” elevator 111. This is a special unit which can lift a cartridge from system 109 up to system 110 or vice versa.
This is done by the picker of system 109 first picking the cartridge to be moved out of its magazine slot and then placing the cartridge on a lift fixture inside the pass-thru elevator 111. The elevator then moves the entire lift fixture upwards until the cartridge can be reached by the picker of system 110. This picker then grabs the cartridge and either inserts it into one of the tape drives in system 110 or into a spare magazine slot of system 110.
The customer may add additional units on top of system 110 in order to increase capacity and performance of his or her system even further. In this case, an additional pass-thru elevator is also added on the back of the new unit to allow cartridges to be moved between all three system units.
While such a system as described above allows the user to increase capacity and performance outside the limits given by the fixed size unit, it is from a cost point-of-view not very effective. Each automation unit contains all the normal elements required for an automation unit (including a picker) and in addition there is the cost of the pass-thru elevator.
For very low end systems, it would be desirable to be able to have a low cost automation unit which can easily be expanded both with respect to number of cartridges and number of tape drives.